1. Field of the Invention
This invention relates to a method and apparatus for managing accesses to a shared, randomly accessed communications channel.
2. Discussion of the Related Art
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Recently, the popularity of wireless local area networks (“WLANs”), such as Wi-Fi and WiMAX networks, has surged. WLANs now provide data connectivity in places such as offices, homes, campuses, and supermarkets. Moreover, WLANs are also becoming an integral part of many next-generation communication networks, such as 3G networks. A WLAN typically operates without completely centralized control of accesses to a shared wireless channel, which is typically referred to as distributed scheduling or random access scheduling. In random access scheduling, the nodes (wireless telephones or computers, for example) of a local contention neighborhood compete for access to the shared channel. More specifically, the individual nodes determine for themselves when and if to attempt to access the channel. As such, two or more nodes may attempt to transmit to the channel at the same time. When this happens, the transmissions may interfere with each other, or collide, which can jumble one or both transmissions, and prevent a receiver (a WLAN access point, for example) from determining the complete context of either transmission. Consequently, the failed transmissions typically have to be resent, which effectively reduces the available bandwidth of the shared wireless channel. For example, if two nodes within a local contention neighborhood are each attempting to communicate with a third node (an access point, for example) ninety-five percent of the time (i.e., each of the nodes has an access attempt percentage of ninety-five percent), ninety percent or more of the potential bandwidth of the wireless channel could be lost to collisions, because at the least both nodes will be transmitting ninety percent of the time. In other words, since each node is transmitting all of but five percent of the time, the largest amount of time that one, but not both, of the nodes could be transmitting is ten percent, which could then lead to collisions the other ninety percent of the time. Alternatively, if the two nodes are only attempting to transmit to the access point five percent of the time (an access attempt percentage of five percent), collisions are unlikely, but the only ten percent (at most) of the possible capacity of the wireless channel will be utilized.
For this reason, one of the challenges in designing and operating a random access wireless network is managing the access attempt percentages for the nodes in the WLAN. If the nodes are instructed to keep their access attempt percentages low, collisions are unlikely but bandwidth is low. Whereas if the nodes are permitted to increase their access attempt percentages at will, the number of collisions can escalate and the available bandwidth of the wireless channel can be negatively affected. Further complicating the assignment of access attempt percentages in a WLAN is the fact that two nodes in communication with different access points can also interfere with one another and cause collisions. Thus, it would be desirable to be able to manage the communication of multiple independent nodes with one or more other nodes or access points such that the shared wireless channel is more efficiently utilized.